In the same way, voting against someone is an act of modesty and realism on the voter’s part. I know things aren’t going to be spectacular if my guy wins; instead, I’m more interested in averting disaster, and hope we can make some reasonable progress along the way. This plays into the human propensity for “loss aversion” — we’re more motivated to avoid losing something than we are to win something, even if the two are the same (like losing or winning the same amount of money). That can make us irrational if we’re at a casino, but it may be helpful when we’re picking a president, especially if the magnitude of the potential loss really is greater than the potential gain.

There’s a related feature of our psychology that also makes us vote against rather than for a candidate: negativity bias. Put simply, we put more stock in the bad than the good. That doesn’t mean we’re all pessimists, but we tend to remember bad things that happen to us for longer than good things, we pay closer attention to negative information, and we’re highly focused on threats to our well-being (which makes perfect sense from an evolutionary standpoint). Some studies have shown that conservatives tend to have a greater negativity bias than liberals, but that doesn’t mean liberals don’t feel it, too.